In wireless network environments such as cellular networks, network entities are provided to facilitate the communication between communicating devices on the network. In Global System for Mobile communications (GSM) networks, Base Station Systems (BSS) are provided on the network, which include one or more Base Transceiver Stations (BTS) and a Base Station Controller (BSC). The BTS manages the radio interface to Mobile Stations (MS) and/or other terminals, and includes the transceivers and antennas to service each cell. A group of BTSs are controlled by a BSC, which provides the control functions and physical links between the Mobile Switching Center (MSC) and the BTS.
The interface between the network and a mobile terminal is often referred to as the radio interface. Radio Resource management (RR) and/or MSC procedures are used to establish, maintain, and release connections that allow a point-to-point dialogue between the network and the terminal. These procedures include “handover” procedures, which generally refers to the passing of a call in progress from one channel or cell to another. An RR element such as the BSC performs high-capacity switching functions, including handover, as well as control of radio frequency (RF) power levels in BTSs.
The first GSM and other analogous networks were designed for voice services. When the user of the GSM data services began, it became evident that the circuit-switched (CS) bearer services were not particularly well suited for certain types of applications, such as those involving date transmissions exhibiting a “bursty” nature. Therefore, in the GSM context, the new packet-switched (PS) data transmission service, General Packet Radio Service (GPRS), was defined for packet services. Generally, GPRS is a packet radio network utilizing the GSM network, which endeavors to optimize data packet transmission by means of GPRS protocol layers on the air interface between a mobile station (or other terminal) and a GPRS network.
If there is no active connection between a terminal and a BSS, the terminal is at rest or in “idle” mode, and the BSS has no specific tasks to perform relative to the terminal. However, the terminal continues to monitor control channels such as the Broadcast Control Channel (BCCH) or the Packet Broadcast Control Channel (PBCCH) of the current and neighboring cells, to facilitate location update operations. In dedicated mode, a physical point-to-point bidirectional RR connection is established. Thus, in dedicated mode, the terminal is allocated dedicated channels for communicating information.
A GPRS mobile station (MS) or other GPRS terminal can operate in one of three modes of operation. A “Class A” mode of operation refers to a mode where the terminal is attached to both GPRS and other GSM services. The mobile user can initiate and/or receive calls on the two services simultaneously. For example, the mobile user can participate in a GSM voice call while simultaneously receiving GPRS data packets. A “Class B” mode of operation refers to a mode where the terminal is attached to both GPRS and other GSM services, but the terminal can only operate one set of services at a time. Another mode of operation, “Class C,” refers to a mode where the terminal can only be attached to either the GSM network or the GPRS network. The selection is performed manually, and there are no simultaneous operations.
Terminals operating in the Class A mode of operation therefore can be attached to both CS and PS services, and can be actively engaged in both services simultaneously. An example of such a Class A mode of operation is the Dual Transfer Mode (DTM) used in GSM/GPRS systems. Other network environments may include analogous modes of operation, such as the Multi Radio Access Bearer (Multi RAB) mode in Wideband Code Division Multiple Access (WCDMA) systems. For example, DTM is applicable for terminals that support GPRS/EGPRS or future analogous systems. A terminal in DTM has resources for an RR connection and is simultaneously allocated resources for one or more temporary block flows (TBFs), provided that the BSS coordinates its allocation of radio resources.
It is noted that during a connection, i.e. when the terminal is in transfer mode such as the “dedicated mode,” power control functions serve to maintain and optimize the radio channel. It is very important that terminals that send data to the network use the proper output power level. If the output power level of the terminal is too low, data throughput may suffer due to errors caused by sub-optimal radio conditions. If the output power level of the terminal is too high, excessive power consumption results, and the data transmission may cause interference to other channels used by other terminals.
In GPRS data transmissions, the terminal determines the appropriate output power levels using specified formulas. These formulas include parameters that the terminal obtains from various sources, namely from system information messages broadcast by the network, or from control messages that are sent specifically to each of the terminals. Such system information messages are transmitted by the network in two possible logical channel structures, depending on the base selected by the network operator. If packet channel structure exists, the system information messages are transmitted on the PBCCH; otherwise the system information messages are transmitted on the BCCH.
As indicated above, the terminal's maximum output power is based on parameters received in system information messages via PBCCH/BCCH while in the (packet) idle mode. When the terminal moves via the dedicated mode to the dual transfer mode the maximum output power may be correct. However when the terminal is in dual transfer mode and it is handed over to a new cell, the terminal is lacking the correct output power parameters of the new cell. The same problem exists if the terminal is in the dedicated mode and it is handed over one or several times to a new cell in which the terminal requests PS resources. The terminal cannot calculate correct output power level for packet switched resources in the new cell while staying in the dedicated mode. Therefore the terminal is not aware of the correct output power and specifically the correct maximum output power for packet transfer when it enters to the dual transfer mode in the target cell.
Accordingly, there is a need in the communications industry for a manner of properly establishing the terminal output power levels in changing circumstances, such as where a terminal is operating in dual transfer mode and a handover occurs. A further need exists for a system and methodology that provides an unintrusive and efficient manner for providing such information, while working within existing protocols and structures. The present invention fulfills these and other needs, and offers other advantages over the prior art.